Since the mid-1970's, the bivalve mollusk (oysters, clams, scallops and related species) aquaculture industry has become increasingly intensified, particularly on the west and east coasts of the United States, and more recently, efforts toward hatchery development are also taking place on the Gulf coast. Previously (and still, in some areas), the edible market industry for these products depended on wild reproduction and natural recruitment into extensively harvested populations. High variability in the supply and quality of natural bivalve seed motivated research and development to establish technology for the intensive management of brood stock, reproduction and rearing of bivalves, at least through early seed stages. Thus today, the industry in many locations on both the west and east coasts is based largely on an intensive agricultural production model, although there are many modes and methods for the grow out of marketable product. However, there remains a very significant need and opportunity to markedly improve the efficiency of various components in the production cycle, as well as address the unique problems inherent for each new species brought into aquaculture.
Although the bivalve shellfish seed production industry, even for the longest cultured species such as oysters, operates on a commercial scale, the consistency of production is still highly variable and a great scope for improvement of efficiency exists. One of the most serious challenges has always been the management of aggressive opportunistic bacterial infections in larval and juvenile cultures. One reason that these diseases have not been uniformly and effectively managed by sanitation and health management procedures is because the bacterial colonization of culture systems remains an uncontrolled variable. Sometimes the benign bacteria colonize the system but often pathogens or a population of bacteria that are antagonistic in some way to the cultured animals establish dominance and result in low productivity and high variability in the success of culture batches.
Opportunistic infections are even more significant in the culture of seed or juvenile bivalves than in larvae. Different shellfish species have variable susceptibility to these bacterial infections. Many, but not all of these infections, are caused by Vibrio spp. (Elston et al. 1999). Elston (1999) identified a variety of instances in which bacterial diseases were causal in larval and seed oyster mortalities. Chronic bacterial diseases of bivalve seed are especially insidious and often go unrecognized as a bacterial disease, even though the cumulative mortality may, in some cases, approach 100% (Elston et al. 1999) and poor growth and discarded substandard seed dramatically compound the losses. In addition, a syndrome of seed oyster losses along the northeast coast of the United States referred to as juvenile oyster disease (JOD), that affects seed of the Eastern oyster, Crassostrea virginica, appears to have a bacterial etiology (Boettcher et al., 2000). Current experience with commercial nursery losses shows that bacterial diseases of the Pacific oyster (Crassostrea gigas), Kumomoto oyster (Crassostrea sikamea), and geoduck clam (Panope abrupta) seed can be highly destructive. The primary mode of pathogen invasiveness, especially for larval and seed oysters, is the progressive growth of bacteria from the oyster shell surface into the soft tissues (Elston et al. 1982, Elston et al. 1999) although there is limited documentation of gastro-intestinal bacterial abscesses (Elston and Leibovitz 1980) and the role of bacteria in the water column and associated with algal cultures is not well understood.
Based on the findings described above, there is a significant need in the art for compositions and methods to treat and or prevent pathogenic bacterial infections in marine orgamsms.